Method of producing a cyclohexenone oxime ether lithium salt, products which can be obtained using this method, the use thereof and corresponding plant protection agents

ABSTRACT

A process for preparing 2-{1-[2-(4-chlorophenoxy)propoxyimino]-butyl}-3-hydroxy-5-(tetrahydrothiopyran-3-yl)cyclohex-2-enone lithium salt by reacting the corresponding acid 2-{1-[2-(4-chlorophenoxy)-propoxyimino]butyl}-3-hydroxy-5-(tetrahydrothiopyran-3-yl)-cyclohex-2-enone and lithium hydroxide and the isolation of the lithium salt are described. Here, it is advantageous to use a solvent mixture which comprises methanol and at least one aromatic hydrocarbon and to remove at least some of the solvent prior to the isolation. It is particularly preferred to dissolve the acid in an aromatic hydrocarbon, preferably toluene, and to use a methanolic lithium hydroxide solution. 
     The product, which can be obtained in a more efficient manner by this process, furthermore has considerable advantages with respect to formulation.

The present invention relates to a process for preparing2-{1-[2-(4-chlorophenoxy)propoxyimino]butyl}-3-hydroxy-5-(tetrahydrothiopyran-3-yl)cyclohex-2-enonelithium salt from the corresponding acid, to products obtainable by thisprocess, to their use and to crop protection compositions comprisingsuch products.

Cyclohexenone oxime ethers and their metal salts are generally known asuseful crop protection agents. They are appreciated in particular asgrass herbicides. Metal salts (WO 97/20807) and in particular thecyclohexenone oxime ether lithium salt of the formula (I)

have been found to be particularly suitable.

In addition to the optimization of the properties of the substance, thedevelopment of an efficient preparation process is of particularimportance with a view to industrial production and use of this activecompound.

For the lithium salt described above, WO 97/20807 refers initially to EP456 112, according to which the corresponding free acid2-{1-[2-(4-chlorophenoxy)propoxyimino]butyl}-3-hydroxy-5-(tetrahydrothiopyran-3-yl)cyclohex-2-enoneis obtained in dissolved form and can then be converted withoutisolation into the lithium salt.

Similarly to the generally customary procedures for preparing such metalsalts by reacting the free acid with a hydride, hydroxide, alkoxide orcarbonate of the desired metal ion, WO 97/20807 describes in anexemplary manner the preparation of the Li salt by reaction of asolution of the cyclohexenone oxime ether in toluene with an aqueouslithium hydroxide solution and subsequent removal of the solid fractionformed. Furthermore, in a further example, the lithium salt is preparedby sodium/lithium exchange. Here, in aqueous solution of thecorresponding cyclohexenone oxime ether sodium salt is reacted with anaqueous lithium chloride solution and the solid fraction is thenseparated off.

In the process mentioned first, problems are encountered when separatingoff the solids fraction formed. Unfavorable filtration properties, inparticular high and varying filter resistance, makes isolation of thesolid on a pilot-plant and production scale and using customaryfiltration apparatus such as pressure nutches or centrifuges extremelydifficult.

The disadvantage of the process based on sodium/lithium exchange isobvious: initially, the free cyclic hexenone oxime ether has to beconverted into the sodium salt in an additional step which is associatedwith yield loss.

It is an object of the present invention to provide a more efficientprocess for preparing the cyclohexenone oxime ether lithium salt, inparticular with a view to the filtration process, the yield and thepurity. We have found that this object is achieved by using a certainsolvent mixture as reaction medium.

Accordingly, the present invention provides a process for preparing2-{1-[2-(4-chlorophenoxy)propoxyimino]butyl}-3-hydroxy-5-(tetrahydrothiopyran-3-yl)cyclohex-2-enonelithium salt of the formula (I),

by reacting2-{1-[2-(4-chlorophenoxy)propoxyimino]butyl}-3-hydroxy-5-(tetrahydrothiopyran-3-yl)cyclohex-2-enoneof the formula (II)

and lithium hydroxide in a solvent mixture and isolating the compound ofthe formula (I),wherein the solvent mixture comprises at least one aromatic hydrocarbonand methanol and at least some of the solvent is removed prior to theisolation.

Surprisingly, the process according to the invention allows a relativelymore efficient isolation of the process product.

The way in which the compounds of the formulae (I), including theformula (I), and (II) are shown includes isomeric forms of thesecompounds. Particular mention may be made of geometrical andstereoisomers, such as cis/trans isomers, enantiomers ordiastereoisomers, and also tautomers, which, in the present case, arebased in particular on the enol structure. Accordingly, the compounds ofthe formula (II), in particular, can also be described ascyclohexane-1,3-dione derivatives. In addition to the substantially pureisomers, the compounds of the formula (I) and (II) also include theirisomer mixtures, for example stereoisomer mixtures.

The starting material for the process according to the invention, thecyclohexenone oxime ether2-{1-[2-(4-chlorophenoxy)-propoxyimino]butyl}-3-hydroxy-5-(tetrahydrothiopyran-3-yl)cyclohex-2-enoneof the formula (II) above can be obtained, for example, by the processesdescribed in WO 97/20807 and EP 456 112. Accordingly, this compound canbe obtained in a manner known per se from2-(1-butyloxy)-3-hydroxy-5-(tetrahydrothiopyran-3-yl)cyclohex-2-enone ofthe formula (III)

and the hydroxylamine 1-aminooxy-2-(4-chlorophenoxy)propane of theformula (IV)

One possible way of reacting these compounds is described, for examplein EP 169 521. The compounds of the formulae (III) and (IV) can also beemployed in the form of their salts, in particular base addition saltsof (III) and acid addition salts of (IV). Suitable salt-forming ions arethe customary ions, for example metal ions and in particular alkalimetal and alkaline earth metal ions, especially sodium, for (III), andhalides and in particular sulfates and hydrogen sulfates for (IV). Thereaction is preferably carried out in an aqueous reaction medium.

Details about the synthesis of the compound of the formula (III) aregiven, in particular, in the documents mentioned in EP 456 112. Therelevant publications are explicitly included herein in their entiretyby way of reference. The compound of the formula (IV) can be synthesizedsimilarly to Houben-Weyl, 10/1 p. 1181 ff.

In its synthesis, the compound of the formula (II) can be isolated aftercustomary work-up of the reaction mixture. However, suitable startingmaterials for the process according to the invention are also mixturesbased on the compound of the formula (II) which are obtained during thesynthesis.

Thus, in a particular embodiment of the process according to theinvention, the compound of the formula (III) or a salt thereof isreacted with the compound of the formula (IV) or a salt thereof and thereaction product is partitioned in an organic solvent or solvent mixturewhich preferably contains an aromatic hydrocarbon, in particular thearomatic hydrocarbon to be used according to the invention. To this end,the organic solvent or solvent mixture may be added even during or afterthe reaction to the preferably aqueous reaction medium. The preferredreaction medium is water or a water-toluene mixture. If required, the pHis adjusted such that the reaction product of the formula (II) issoluble in the organic solvent or solvent mixture. A pH of about 5 to 6has been found to be expedient.

Thus, the starting material used for the process according to theinvention can be a solution of the compound of the formula (II),preferably in an aromatic hydrocarbon and in particular in toluene. Thissolution can, for example, be the organic phase of the reaction mixtureof the above reaction of the compounds (III) and (IV), which, ifrequired, may be concentrated or admixed with more solvent. However, itmay also be the organic phase used, after the conversion leading to thecompound (II) has ended, for extracting the reaction mixture or theresidue obtained following concentration of the reaction mixture, whichorganic phase can be adjusted to a desired concentration of (II) byconcentration or addition of more solvent.

Accordingly, the present invention provides in particular a process forpreparing (I) from (III) and (IV) via a solution of (II) withoutisolating (II) in substance.

According to the invention, the reaction of (II) with lithium hydroxideis carried out in a solvent mixture which comprises methanol and atleast one aromatic hydrocarbon.

It is the purpose of the aromatic hydrocarbon or hydrocarbon mixture todissolve the compound (II). Suitable aromatic hydrocarbons include inparticular solvents from the benzene series, such as alkyl-substitutedbenzenes, for example toluene and xylene. Toluene is especiallysuitable.

If the compound of the formula (II) is obtained in isolated form,initially at least some of the substance may be dissolved in thearomatic hydrocarbon (mixture) and then be contacted as a solution withthe other reactants. If appropriate, it may also be suitable to addsubstance, i.e., for example, the total amount of (II) or a partialamount thereof, to a reaction mixture which already contains aromatichydrocarbon. If the compound of the formula (II) is obtained as asolution, it is possible to use this solution if the solvent does notinterfere with the reaction according to the invention. It may benecessary to add aromatic hydrocarbon to be used according to theinvention to this solution or to the reaction mixture. It may also beuseful to remove at least some of the solvent obtained with the solutionof compound (II), if appropriate with simultaneous addition of aromatichydrocarbon.

Preference is given to using a solution of2-{1-[2-(4-chlorophenoxy)propyloximino]butyl}-5-tetrahydrothiopyran-3-yl-3-hydroxycyclohex-2-en-1-oneof the formula (II) which contains at least one aromatic hydrocarbon.Accordingly, at least some of the compound of the formula (II) isdissolved in an aromatic hydrocarbon or an aromatic hydrocarbon mixture.The solution of the compound (II) used is based on at least one aromatichydrocarbon but may additionally also comprise other solvents. Accordingto a particular embodiment, the solution is a solution of the totalamount of compound (II) to be reacted in an aromatic hydrocarbon,preferably toluene.

It may be advantageous to adjust the concentration of the cyclohexenoneoxime ether (II) to a desired value. If a solution of the compound (II)is used, the concentration of the compound of the formula (II) ispreferably from 5 to 40% by weight, with preference from 10 to 30% byweight and in particular about 20% by weight, based on the total weightof the solution to be used. Thus, a preferred embodiment of the presentinvention relates to the use of a corresponding toluene solutionobtainable, in particular, by adding solvent to a pre-concentrate havinga higher concentration of cyclohexenone oxime ether (II).

Lithium hydroxide (LiOH) is generally obtained as a solid. It can beused, for example, in anhydrous form or as hydrate, in particular asmonohydrate. Commercially available are, for example, calcined lithiumhydroxide or lithium hydroxide monohydrate. These substances are usuallyavailable in a chemical purity of at least 98%. For economical reasons,the use of lithium hydroxide monohydrate may be particularly suitable.At least some of the solid can initially be dissolved in methanol, amethanol-containing solvent or another solvent, for example water, andcan then be brought into contact as a solution with the other reactants.If appropriate, it may also be possible to add a solid, i.e., forexample, the total amount of LiOH or a partial amount thereof as solidto a reaction mixture in which methanol is already present.

Preference is given to reacting a solution of LiOH which containsmethanol. Accordingly, at least some of the LiOH is dissolved inmethanol or a methanol-containing solvent mixture. What is used is asolution of LiOH which is based on methanol but which may, in additionto methanol, also comprise other solvent. Preference is given tomethanolic LiOH solutions which, in addition to possible furthersolvents, comprise at least 70% by weight, preferably at least 80% byweight and in particular at least 85% by weight of methanol, based onthe total amount of solvent in the LiOH solution used. Other possiblesolvents are, in particular, water and lower alcohols, such as ethanol,propanol and isopropanol. According to a particular embodiment, thesolution used is a solution of the total amount of LiOH to be reacted inmethanol.

A methanolic LiOH solution advantageously comprises 1 to 7% by weight,preferably 2 to 6% by weight and in particular about 5% by weight ofLiOH. The amounts stated are based on the total weight of the solutionused, prior to the addition.

The cyclohexenone oxime ether Li salt (I) is obtained by reactingcyclohexenone oxime ether (II) with lithium hydroxide. To this end, thereactants are at least partially dissolved.

As discussed above, it may be advantageous from a technical point ofview to initially prepare appropriate solutions and then to bring thesolutions into contact with one another, i.e. generally to mix them witheach other. However, it is also possible to generate suitable solutionsquasi in situ.

Expediently, either the cyclohexenone oxime ether (II) is initiallycharged, in particular as a solution, and lithium hydroxide is added, inparticular as a solution, or conversely lithium hydroxide is initiallycharged and the cyclohexenone oxime ether (II) is added. It is alsopossible to add both reactants simultaneously, in particular assolutions, if appropriate to an initial charge of some of the respectivesolution(s) or of solvent. The addition may take place all at once, alittle at a time or continuously. What is obtained is the solventmixture according to the invention which comprises at least one aromatichydrocarbon, methanol and, if appropriate, further solvents, for examplewater. During the course of the reaction, (more) water is formed.

To ensure complete conversion, the lithium hydroxide solution is usuallyemployed in a molar excess. Preference is given to using a molar excessof from 0.5 to 10%, based on the cyclohexenone oxime ether (II) used asstarting material. However, it may also be good practice to reactlithium hydroxide in a molar ratio of 1:1 with the cyclohexenone oximeether (II). In this case, for example, the addition of LiOH, inparticular as lithium hydroxide solution, may be monitored using asuitable pH electrode and the metered addition may be continued untilthe equivalents point is reached.

The duration of the metered addition of the reaction partners inquestion is usually in the range from 10 minutes to 360 minutes,preferably from 10 minutes to 120 minutes, in particular about 30minutes.

Once all reactants have been added, stirring may be continued until thereaction has gone to completion.

The reaction is usually carried out at temperatures of from −20° C. to60° C., preferably 0–40° C., particularly preferably 20–30° C.

Prior to the isolation of the cyclohexenone oxime ether salt (I), atleast some of the solvent mixture is removed. In particular, methanol isremoved from the solvent mixture. This is generally removed togetherwith other components of the solvent mixture, in particular as amethanol/toluene/water mixture.

Removal is preferably carried out by distillation, usually attemperatures between 20 and 70° C., preferably at 30–60° C. andparticularly preferably at 40–50° C.

The distillation can be carried out under atmospheric pressure or,preferably, under reduced pressure.

According to a preferred embodiment, the temperature in the reactor issubstantially kept constant during the distillation. In this case, it isnecessary to vary the pressure when distilling an azeotrope, for examplethe methanol/toluene/water mixture which is preferred according to theinvention. The variation of the pressure is carried out in a mannerknown per se by the person skilled in the art.

The removal of solvent serves in particular to reduce the amount ofdissolved cyclohexenone oxime ether lithium salt (I). The cyclohexenoneoxime ether lithium salt (I) precipitates out. It forms a suspension.Accordingly, it may be good practice to remove such an amount of solventthat the compound of the formula (I) precipitates out substantiallycompletely.

According to a particular aspect, the methanol is removed from thereaction mixture substantially completely. Once this has been achieved,the removal of solvent can be stopped. However, it may also be goodpractice to terminate the removal even earlier. It has been found to beexpedient to add fresh methanol to the suspension once the removal ofmethanol has been terminated. The amount that is to be added should besuch that as little as possible and preferably substantially no productredissolves. Typically, from 1 to 100 g, preferably from 5 to 50 g andin particular from 20 to 35 g of methanol may be added per mole ofcyclohexenone oxime ether (II).

The cyclohexenone oxime ether lithium salt (I) is usually isolated bysubjecting the resulting suspension to a solid/liquid separation. Forthis purpose, the person skilled in the art has a large number ofsuitable separation methods at their disposal, in particularsedimentation and filtration steps. Preference is given to filtration,in particular filtration under pressure, belt filtration, vacuumfiltration, centrifugation, and the like. In the process according tothe invention, the filtration steps can be carried out relativelyadvantageously since the filter resistances encountered here arerelatively low, which allows adequate filtration times to be achieved.

It is generally expedient to purify the solid that has been separatedoff, in particular in the form of a filter cake. To this end, the solidmay be washed with a suitable solvent. Suitable solvents are aromatichydrocarbons such as benzene, toluene and xylene, aliphatichydrocarbons, such as pentane, hexane, heptane, petroleum ether, ligroinand cyclohexane, halogenated hydrocarbons, such as dichloromethane,carbon tetrachloride and chlorobenzene, ethers, such as diethyl ether,ethyl-n-propyl ether, di-n-butyl ether, diisopropyl ether,tert-butyl-methyl ether, di-isoamyl ether, cyclohexyl methyl ether,ethylene glycol dimethyl ether, diethylene glycol dimethyl ether,tetrahydrofuran, dioxane, anisol and phenetol, ketones, such as acetoneand methyl ethyl ketone, nitriles such as acetonitrile, butyronitrileand benzonitrile, sulfoxides and sulfones, such as dimethylsulfoxide andsulfolane, amides, such as formamide, methylformamide anddimethylformamide, or alcohols, such as methanol, ethanol, propanol,isopropanol, n-butanol, isobutanol, sec-butanol or tert-butanol. It isalso possible to use mixtures of these solvents. Particularly suitableis the aromatic hydrocarbon which has already been used for thereaction.

The solvent used for washing can initially be used for rinsing thereaction apparatus, in particular the container, and then be passedthrough the filter cake, if required a little at a time.

In general, it is also expedient to dry the solid that has beenseparated off, in particular the filter cake. This may usually becarried out in vacuum drying cabinets, paddle dryers and other deviceswhich serve the same purpose. However, it is also possible to dry thefilter cake directly on the filter. This can be carried out, forexample, by blow drying using an inert gas such as nitrogen or argon,which may be heated, if required.

The present invention also provides the product which is obtainable bythe process according to the invention, i.e. substantially2-{1-[2-(4-chlorophenoxy)propoxyimino]butyl}-3-hydroxy-5-(tetrahydrothiopyran-3-yl)cyclohex-2-enonelithium salt of the formula (I). The term “substantially” is meant to beunderstood according to the invention as generally meaning a percentageof at least 90%, preferably at least 95% and in particular at least 98%.In this context, the term describes the content of2-{1-[2-(4-chlorophenoxy)propoxyimino]butyl}-3-hydroxy-5-(tetrahydrothiopyran-3-yl)cyclohex-2-enonelithium salt of the formula (I) based on the total weight of the productobtainable. A particular form of product obtainable according to theinvention has a content of (I) of at least 96% by weight, preferably atleast 97% by weight and in particular at least 98% by weight, based onthe total weight of the product obtained. Advantageously, the content oforganic compounds derived from the compound of the formula (I) and, inthe further sense, also from compounds of formulae (II), (III) and/or(IV) is less than 2% by weight and preferably less than 1% by weight.

The present invention also provides crop protection compositionscomprising2-{1-[2-(4-chlorophenoxy)propoxyimino]butyl}-3-hydroxy-5-(tetrahydrothiopyran-3-yl)cyclohex-2-enonelithium salt, preparable by the process according to the invention.Depending on the intended use, the compositions comprise one or moreother active compounds, in particular crop protection agents, and/orcustomary auxiliaries.

The cyclohexenone oxime ether lithium salt (I) or the compositionscomprising it can be used, for example, in the form of ready-to-sprayaqueous solutions, powders, suspensions, also highly-concentratedaqueous, oily or other suspensions or dispersions, emulsions, oildispersions, pastes, dusts, materials for broadcasting, or granules, bymeans of spraying, atomizing, dusting, broadcasting or watering. The useforms depend on the intended aims; in each case, they should ensure avery fine distribution of the salt (I) according to the invention.

Suitable inert additives are essentially: mineral oil fractions ofmedium to high boiling point, such as kerosene and diesel oil,furthermore, coal tar oils and oils of vegetable or animal origin,aliphatic, cyclic and aromatic hydrocarbons, e.g. paraffin,tetrahydronaphthalene, alkylated naphthalenes and their derivatives,alkylated benzenes and their derivatives, alcohols, such as methanol,ethanol, propanol, butanol and cyclohexanol, ketones such ascyclohexanone, strongly polar solvents, e.g. amines such asN-methylpyrrolidone and water.

Aqueous use forms can be prepared from emulsion concentrates,suspensions, pastes, wettable powders, water-dispersible granules byadding water. To prepare emulsions, pastes or oil dispersions, thesubstances, either as such or dissolved in an oil or solvent, can behomogenized in water by means of a wetting agent, tackifier, dispersantor emulsifier. Alternatively, it is possible to prepare concentratescomprising active substance, wetting agent, tackifier, dispersant oremulsifier and, if appropriate, solvent or oil, which are suitable fordilution with water.

Suitable surfactants (adjuvants) are the alkali metal salts, alkalineearth metal salts and ammonium salts of aromatic sulfonic acids, e.g.ligno-, phenol-, naphthalene- and dibutylnaphthalene sulfonic acid, andof fatty acids, alkyl- and alkylaryl sulfonates, alkyl sulfates, laurylether sulfates and fatty alcohol sulfates, and salts of sulfated hexa-,hepta- and octadecanoles, and also of fatty alcohol glycol ethers,condensates of sulfonated naphthalene and its derivatives withformaldehyde, condensates of naphthalene, of the naphthalene sulfonicacids, with phenol and formaldehyde, polyoxyethylene octyl phenol ether,ethoxylated isooctyl-, octyl- or nonylphenol, alkylphenyl ortributylphenyl polyglycol ether, alkylaryl polyether alcohols,isotridecyl alcohol, fatty alcohol/ethylene oxide condensates,ethoxylated castor oil, polyoxyethylene alkyl ethers or polyoxypropylenealkyl ethers, lauryl alcohol polyglycol ether acetate, sorbitol esters,lignosulfide waste liquors or methyl cellulose.

Powders, materials for broadcasting and dusts can be prepared by mixingor grinding the active substances together with a solid carrier.

Granules, e.g. coated granules, impregnated granules and homogeneousgranules, can be prepared by binding the active compounds to solidcarriers. Solid carriers are mineral earths, such as silicas, silicagels, silicates, talc, kaolin, limestone, lime, chalk, bole, loess,clay, dolomite, diatomaceous earth, calcium sulfate, magnesium sulfate,magnesium oxide, ground synthetic materials, fertilizers such asammonium sulfate, ammonium phosphate and ammonium nitrate, ureas, andproducts of vegetable origin, such as cereal meal, tree bark meal, woodmeal and nutshell meal, cellulose powders, or other solid carriers.

The lithium salt and, if appropriate, other active compounds may bepresent in the compositions in dissolved or undissolved, in particularsolid, for example particulate form.

The concentration of the active compound (I) in the ready-to-usepreparations may vary within wide ranges, for example from 0.001 to 98%by weight, preferably from 0.01 to 95% by weight. The active compoundsare employed in a purity of from 90% to 100%, preferably from 95% to100% (according to the NMR spectrum).

According to a particular embodiment, the crop protection compositioncomprises

-   from 1 to 70% by weight of    2-{1-[2-(4-chlorophenoxy)propoxyimino]butyl}-3-hydroxy-5-(tetrahydrothiopyran-3-yl)cyclohex-2-enone    lithium salt;-   from 0 to 40% by weight of at least one further active compound; and-   from 0 to 99% by weight of customary auxiliaries.

To widen the spectrum of action and to achieve synergistic effects, thecyclohexenone oxime ether lithium salt (I) may be mixed with a largenumber of representatives of other herbicidal or growth-regulatingactive compound groups and applied concomitantly. Suitable componentsfor mixtures are, for example, 1,2,4-thiadiazoles, 1,3,4-thiadiazoles,amides, aminophosphoric acid and its derivatives, amino triazoles,anilides, aryloxy/heteroaryloxyalkanoic acids and their derivatives,benzoic acid and its derivatives, benzothiadiazinones,2-(hetaroyl/aroyl)-1,3-cyclohexanediones, heteroaryl aryl ketones,benzylisoxazolidinones, meta-CF₃-phenyl derivates, carbamates, quinolinecarboxylic acid and its derivatives, chloroacetanilides, furthercyclohexane-1,3-dione derivates, diazines, dichloropropionic acid andits derivatives, dihydrobenzofurans, dihydrofuran-3-ones,dinitroanilines, dinitrophenols, diphenyl ethers, dipyridyles,halocarboxylic acids and their derivatives, ureas, 3-phenyl uracils,imidazoles, imidazolinones, N-phenyl-3,4,5,6-tetrahydrophthalimides,oxadiazoles, oxiranes, phenols, aryloxy- andheteroaryloxyphenoxypropionic esters, phenyl acetic acid and itsderivatives, 2-phenyl propionic acid and its derivatives, pyrazoles,phenylpyrazoles, pyridazines, pyridinecarboxylic acid and itsderivatives, pyrimidyl ethers, sulfonamides, sulfonyl ureas, triazines,triazinones, triazolinones, triazolcarboxamides and uracils.

Particularly suitable areN-(butoxymethyl)-2-chloro-N-(2,6-diethylphenyl)acetamide (common name:butachlor), 2-(1,3-benzothiazol-2-yloxy)-N-methyl acetanilide (commonname: mefenacet), 3,7-dichloroquinoline-8-carboxylic acid (common name:quinclorac), α-(4,6-dimethoxypyrimidin-2-yl-carbamoylsulfamoyl)-o-toluicacid methyl ester (common name: bensulfuronmethyl),3-isopropyl-1H-2,1,3-benzothiadiazin-4-(3H)one 2,2-dioxide (common name:bentazone), N-(ethylthiocarbonyl)azepan (common name: molinate),4-chlorobenzothio N,N-diethylcarbamate (common name: thiobencarb),N-(2-propoxyethyl)-2-chloro-N-(2,6-diethylphenyl)acetamide (common name:pretilachlor),3,5-bis(methylthiocarbonyl)-2-difluoromethyl-4-(2-methylpropyl)-6-trifluoromethylpyridine(common name: dithiopyr), ethyl2-[4-(6-chlorobenzoxazol-2-yloxy)phenoxy]propionate (common name:fenoxapropethyl), N-(2-phenylprop-2-yl-thiocarbonyl)piperidine (commonname: dimepiperate),4-(2,4-dichlorobenzoyl)-1,3-dimethylpyrazol-5-yltoluyl-4-sulfonate(common name: pyrazolynate, pyrazolate),2-[4-(2,4-dichlorobenzoyl)-1,3-dimethylpyrazol-5-yloxy]acetopheno ne(common name: pyrazoxyfen),2-[4-(2,4-dichloro-m-toluyl)-1,3-dimethylpyrazol-5-yloxy]-4′-methylacetophenone (common name: benzofenap),2-(2-naphthyloxy)propionanilide (common name: naproanilid), methyl5-(4,6-dimethoxypyrimidin-2-yl-carbamoylsulfamoyl)-1-methylpyrazo1-4-carboxylate (common name: pyrazosulfuronethyl),1-(4,6-dimethoxy-1,3,5-triazin-2-yl)-3-[2-(2-methoxyethoxy)phenylsulfonyl] urea (common name: cinosulfuron),2-bromo-3,3-dimethyl-N-(1-methyl-1-phenylethyl)butyramide (common name:bromobutide), 1-(1-methyl-1-phenylethyl)-3-p-toluyl urea (common name:dymron, daimuron),N²-(1,2-dimethylpropyl)-N⁴-ethyl-6-methylthio-1,3,5-triazin-2,4-di amine(common name: dimethametryn), S-benzyl1,2-dimethylpropyl(ethyl)thiocarbamate (common name: esprocarb),(Z)-N-but-2-enyloxymethyl-2-chloro-2′,6′-diethylacetanilide (commonname: butenachlor), S-2-methylpiperidinocarbonylmethyl O,O-dipropylphosphorodithionate (common name: piperophos),(1RS,2SR,4SR)-1,4-epoxy-p-menth-2-yl 2-methylbenzyl ether (common name:cinmethylin), N-(3,4-dichlorophenyl)propanamide (common name: propanil),α-chloro-N-(3-methoxy-2-thienyl)methyl-2′,6′-dimethylacetanilide,4-ethoxybenz-2′,3′-dihydrochloranilide,1-diethylcarbamoyl-3-(2,4,6-trimethylphenylsulfonyl)-1,2,4-triazole,3-(2-chlorophenylmethyl)-1-(1-methyl-1-phenylethyl) urea,2-(2-chloro-4-mesylbenzoyl)cyclohexan-1,3-dione,2,4-dichlorophenoxyacetic acid (common name: 2,4-D),N-(2-chloroimidazole[1,2-a]pyridin-3-yl-sulfonyl)-N′ urea(4,6-dimethoxy-2-pyrimidyl) (common name: imazosulfuron),1-{[2-(cyclopropylcarbonyl)phenyl]aminosulfonyl}-3-(4,6-dimethoxypyrimidin-2-yl)urea,1-(4,6-dimethoxypyrimidin-2-yl)-3-[1-methyl-4-(2-methyl-2H-tetrazol-5-yl)pyrazol-5-ylsulfonyl]urea, 4-(4-chloro-2-methylphenoxy)butyric acid (common name: MCPB),2,4-bis(ethylamino)-6-methylthio-1,3,5-triazine (common name:simetryne), 1-[(4,6-dimethoxypyrimidin-2-yl)-3-(2-ethoxyphenoxysulfonyl)urea (common name: ethoxysulfuron).

Further active compounds include, in particular, metal salts of the cropprotection agent quinclorac or the aromatic carboxylic acid of theformula (V)

where M is a monovalent (n=1) or divalent (n=2) metal cation.

It may furthermore be advantageous to employ the cyclohexenone oximeether lithium salt (I), alone or in combination with other herbicides,in the form of a mixture with other crop protection agents, for exampletogether with agents for controlling pests or phytopathogenic fungi orbacteria. Also of interest is the miscibility with mineral saltsolutions, which are employed for treating nutritional and trace elementdeficiencies. Non-phytotoxic oils and oil concentrates may also beadded.

The use of2-{1-[2-(4-chlorophenoxy)propoxyimino]butyl}-5-tetrahydrothiopyran-3-yl-3-hydroxycyclohex-2-en-1-onelithium salt preparable by the process according to the invention asherbicide is also provided by the present invention. This relates to theuse as crop protection agent in agriculture, if appropriate incombination with other crop protection agents and/or fertilizers.

Depending on the application method used in each case, the Li salt (I)can be used in a large number of crop plants and ornamental plants foreliminating undesirable plants. Examples of suitable crops are thefollowing:

Allium cepa, Ananas comosus, Arachis hypogaea, Asparagus officinalis,Beta vulgaris spp. altissima, Beta vulagris spp. rapa, Brassica napusvar. napus, Brassica napus var. napobrassica, Brassica rapa var.silvestris, Camellia sinensis, Carthamus tinctorius, Caryaillinoinensis, Citrus limon, Citrus sinensis, Coffea arabica (Coffeacanephora, Coffea liberica), Cucumis sativus, Cynodon dactylon, Daucuscarota, Elaeis guineensis, Fragaria vesca, Ficus elastica, Glycine max,Gossypium hirsutum, (Gossypium arboreum, Gossypium herbaceum, Gossypiumvitifolium), Helianthus annuus, Hevea brasiliensis, Hordeum vulgare,Humulus lupulus, Ipomoea batatas, Juglans regia, Lens culinaris, Linumusitatissimum, Lycopersicon lycopersicum, Malus spp., Manihot esculenta,Medicago sativa, Musa spp., Nicotiana tabacum (N. rustica), Oleaeuropaea, Oryza sativa, Phaseolus lunatus, Phaseolus vulgaris, Piceaabies, Pinus spp., Pisum sativum, Prunus avium, Prunus persica, Pyruscommunis, Ribes sylestre, Ricinus communis, Saccharum officinarum,Secale cereale, Solanum tuberosum, Sorghum bicolor (S. vulgare),Theobroma cacao, Trifolium pratense, Triticum aestivum, Triticum durum,Vicia faba, Vitis vinifera, Zea mays.

The preferred use is the use as rice herbicide.

Furthermore, the cyclohexenone oxime ether lithium salt (I) can also beused in crops which tolerate the action of herbicides.

The salt (I) according to the invention or its preparation can beapplied pre- or post-emergence, preferably by foliar treatment. If theactive compound is less well tolerated by certain crop plants,application techniques may be used in which the compositions aresprayed, with the aid of the spraying equipment, in such a way that theycome into as little contact as possible, if any, with the leaves of thesensitive crop plants, while the active compound reaches the leaves ofthe undesirable plants growing underneath, or the bare soil surface(post-directed, lay-by).

The rates of application of active compound (I) are from 0.001 to 3.0,preferably from 0.01 to 1.0, kg/ha of active substance (a.s.), dependingon the control target, the season, the target plants and the growthstage. Application can be carried out by customary spraying techniquesusing, for example, water as carrier and amounts of about 100 to 1000 lof spray liquor/ha. Application of the herbicidal compositions by the“low volume” or “ultra-low-volume” process is possible, as is theirapplication in the form of granules.

The cyclohexenone oxime ether Li salt (I) preparable by the processaccording to the invention surprisingly forms comparatively stable SCformulations, in particular oil SC formulations. This is of importanceespecially when the salt is used as rice herbicide and, according to afurther aspect, for use in tropical regions. Here, it is advantageous ifa comparatively high long-term storage stability at an elevatedtemperature in the range from 30 to 40° C. can be ensured.

The invention is illustrated in more detail by the examples below.

PREPARATION EXAMPLES Example 1

Product Used: Calcined LiOH (Process A)

At 25° C., 702.78 g (0.400 mol) of a 26.5% strength solution of thecyclohexenone oxime ether (II) in toluene are initially charged withstirring and diluted with 229.47 g of toluene, thus adjusting theconcentration of the cyclohexenone oxime ether (II) to 20%. 200.98 g(0.420 mol) of a 5% strength LiOH solution (calcined LiOH (98+);Chemetall) in MeOH are then introduced over a period of 30 min. Themixture is stirred at 25° C. for 1 h. 370.59 g of a MeOH/toluene/watermixture are then distilled off at 50° C. under reduced pressure. Duringthe distillation, the temperature is kept at 50° C. and the pressure isreduced in a controlled fashion from 450 mbar to 200 mbar. Thedistillation time is 210 min. Once the distillation has ended, 13 g ofmethanol are added, the mixture is stirred at room temperature for 15min and the suspension is discharged from the stirred vessel onto apressure nutsche. When the filtration has ended, the stirred vessel isrinsed with 174.00 g (200 ml) of fresh toluene and the filter cake iswashed with this toluene. The filter cake is then washed twice with ineach case 87.0 g (100 ml) of fresh toluene. The filter cake is thendried at 50° C. in a vacuum drying cabinet for 24 h. This gives 181.01 gof filter cake with a content of 98.2%. Taking this content intoaccount, the yield is 94.1%.

Example 2

Product Used: LiOH Monohydrate (Process B)

At 25° C., 770.73 g (0.400 mol) of a 24.2% strength solution of thecyclohexenone oxime ether (II) in toluene are initially charged withstirring and diluted with 161.84 g of toluene, thus adjusting theconcentration of the cyclohexenone oxime ether (II) to 20%. 200.99 g(0.420 mol) of a 8.8% strength LiOH monohydrate solution in MeOH(Chemetall; corresponds to a 5% strength solution based on LiOH (100%))are then introduced over a period of 30 min. The mixture is stirred at25° C. for 1 h. 381.21 g of a MeOH/toluene/water mixture are thendistilled off at 50° C. under reduced pressure. During the distillation,the temperature is kept at 50° C. and the pressure is reduced in acontrolled fashion from 450 mbar to 200 mbar. The distillation time is230 min. Once the distillation has ended, a dash of methanol is addedand the suspension is discharged from the stirred vessel onto a pressurenutsche. When the filtration has ended, the stirred vessel is rinsedwith 174.00 g (200 ml) of fresh toluene and the filter cake is washedwith this toluene. The filter cake is then washed twice with in eachcase 87.0 g (100 ml) of fresh toluene. The filter cake is then dried at50° C. in a vacuum drying cabinet for 24 h. This gives 189.60 g offilter cake with a content of 96.5%. Taking this content into account,the yield is 97.0%.

Filtration Properties and Yields

Example 3

Determination of the Filter Resistances and the Filtration Times

The suspension of the lithium salt in toluene obtained after thedistillation is charged to a 2.2 l pressure filter made of Hastelloy C 4having a filter surface of 20 cm² and a filter cloth made ofpolypropylene (PP 2703). The pressure filter is then closed and afiltration pressure of 1 bar is applied. During the filtration, thepressure is kept constant and the time to gas breakthrough is measured.Finally, the filter is vented and opened and the thickness of the cakeis measured.

Table 1 shows, in a comparative manner, filter resistances, filtrationtimes and yields for the cyclohexenone oxime ether lithium salts (I)prepared by the processes mentioned.

The filter resistance α*η stated in Table 1 is calculated using theformula:α*η=2*t _(F)*filter surface*filtration pressure*volume of thefiltrate⁻¹*thickness of the filter cake⁻¹

TABLE 1 Filter resistances and filtration times Filter resistancesFiltration Process Experiment α*η (mPas/M²) time t_(F)(s) Yield (%)Comparative Process A 1. Experiment 2.2 × 10¹³ 7274 95.9% cyclohexenoneoxime 2. Experiment 5.6 × 10¹³ 18315 94.9% ether (II) + LiOH/H₂O 3.Experiment 2.0 × 10¹⁴ 65410 94.2% (see Preparation Exam- ple 6 of WO97/20807) Comparative Process B 1. Experiment 3.8 × 10¹¹ 138 89.8cyclohexenone oxime 2. Experiment 4.1 × 10¹¹ 151 90.2 ether Na salt +LiCl (see Preparation Exam- ple 9 of WO 97/20807) Process A accordingto 1. Experiment 3.2 × 10¹¹ 103 94.1 the invention 2. Experiment 3.9 ×10¹¹ 115 94.5 cyclohexenone oxime 3. Experiment 3.6 × 10¹¹ 102 93.8ether (II) + LiOH (98%) in MeOH (see Prepara- tion Example 1). Process Baccording to 1. Experiment 3.5 × 10¹¹ 107 97.0 the invention 2.Experiment 2.1 × 10¹¹ 56 96.7 cyclohexenone oxime 3. Experiment 3.7 ×10¹¹ 130 95.9 ether (II) + LiOH mono- hydrate (57%) in MeOH (seePreparation Exam- ple 2) The best filtration properties and yields areobtained when the cyclohexenone oxime ether Li salts (I) are prepared bythe processes according to the invention according to Example 1 and 2.Oil SC Formulations

Example 4

General Experimental Description of the Preparation of Oil SCFormulations

Using glass beads (diameter: 0.9–1.2 mm) as an aid for grinding, thelithium salts (I) are ground at about 0° C. with the lipophilicsolvents—here generally liquid media which have little if any solventpower with respect to the active compound salts. The active compoundconcentration is about 10–30%, generally 20%.

Grinding is carried out in a Dyno-mill from Bachofen using a batch sizeof from 0.5 to 1 liter in a passage operation. In general after 5passages (the slurry being pumped through the mill with the aid of aroller pump) mean particle sizes of 1–3 μm are achieved, according tomicroscopic evaluation.

Incorporation and dilution with further auxiliaries according to therecipes given below is then carried out by homogenizing for 10 minutesusing a ground-glass or magnetic stirrer.

Practice of the Experiments

90% of the solvent (esters and/or aromatic solvents) and the auxiliariesstated (emulsifiers and dispersants) are initially charged according tothe recipe given below, which is in each case identical, and the activecompound (I) is added as a solid powder.

The formulation batch is then made up to 1 l (typical batch size) usingthe remaining solvent.

The batch is then ground as described above in a Dyno-mill using passageoperation until about 60% of the particles have a size of less than 2 μm(microscopic evaluation). Typically, this requires 5 passages.

Recipe:  75 g/l of(I) 250 g/l of Aerosol OT-A  50 g/l of Emulpon EL 20500 g/l of methyl oleate ad 1 l Solvesso 150

Table 2 shows stability data of the cyclohexenone oxime ether Li salts(I) prepared by the individual processes.

TABLE 2 Oil SC storage stability in % (rel.) after 14–28 d at 54° C. 2Weeks 4 Weeks Process 54° C. 54° C. Comparative Process A 93.4 88.2cyclohexenone oxime ether (II) + LiOH/H₂O (see Preparation Exam- ple 6of WO 97/20807) Comparative Process B 94.2 91.2 cyclohexenone oximeether Na salt + LiCl (see Preparation Exam- ple 9 of WO 97/20807)Process A according to 95.6 94.8 the invention cyclohexenone oxime ether(II) + LiOH (98%) in MeOH

It is found that, after a storage time of 4 weeks at 54° C., the lithiumsalt prepared by process A according to the invention, for example, hasconsiderably better storage stability than a comparable lithium saltprepared according to the prior art.

1. A process for preparing2-{1-[2-(4-chlorophenoxy)propoxyimino]butyl}-3-hydroxy-5-(tetrahydrothiopyran-3-yl)cyclohex-2-enonelithium salt of the formula (I),

by reacting2-{1-[2-(4-chlorophenoxy)propoxyimino]butyl}-3-hydroxy-5-(tetrahydrothiopyran-3-yl)cyclohex-2-enone of the formula (II)

and lithium hydroxide in a solvent mixture and isolating the compound ofthe formula (I), wherein the solvent mixture comprises at least onearomatic hydrocarbon and methanol and at least some of the solvent isremoved prior to the isolation.
 2. A process as claimed in claim 1,wherein the aromatic hydrocarbon used is toluene.
 3. A process asclaimed in claim 1, wherein the solution of the compound of the formula(II) comprises the compound in a concentration of from 5 to 40% byweight.
 4. A process as claimed in claim 1, wherein the lithiumhydroxide solution comprises LiOH in a concentration of from 1 to 7% byweight.
 5. A process as claimed in claim 1, wherein the reaction iscarried out at a temperature of from −2° C. to 60° C.
 6. A process asclaimed in claim 1, wherein the solvent is removed by distillation.
 7. Aprocess as claimed in claim 6, wherein the distillation is carried outat temperatures of from 20° C. to 70° C.
 8. A process as claimed inclaim 6, wherein the distillation is carried out at a substantiallyconstant temperature.
 9. A process as claimed in claim 6, wherein suchan amount of solvent is removed that the compound of the formula (I)precipitates out substantially completely.
 10. A process as claimed inclaim 1, wherein the isolation is carried out by filtration orcentrifugation.
 11. A process as claimed in claim 3, wherein theconcentration of the compound of the formula (II) is from 10 to 30% byweight.
 12. A process as claimed in claim 3, wherein the concentrationof the compound of the formula (II) is about 20% by weight.
 13. Aprocess as claimed in claim 4, wherein the lithium hydroxideconcentration is from 2 to 6% by weight.
 14. A process as claimed inclaim 4, wherein the lithium hydroxide concentration is about 5% byweight.
 15. A process as claimed in claim 5, wherein the reactiontemperature is from 0° C. to 40° C.
 16. A process as claimed in claim 5,wherein the reaction temperature is from 20° C. to 30° C.
 17. A processas claimed in claim 7, wherein the distillation temperature is from 30°C. to 60° C.
 18. A process as claimed in claim 7, wherein thedistillation temperature is from 40° C. to 50° C.